Machine and method for the production of blasting detonators and improved blasting detonators



P. c. BISHOP 2,773,410

QDUCTION OF BLASTING ORS NAT

2 Shoots-Sheet l v N at ATTOQNEYS Dec. 11, 1956 MACHINE AND METHOD FORTHE PR DETONATORS AND IMFROVED BLASTING DETO Filed lay 22, 1951 Dec. 11,1956 P. c. BISHOP 2,773,410

mums AND ua'mon FOR E paooucnou 0F sms'rmc omounoas mo mm o suxsmcosromoas Filed lay 22, 1951 2 Sheets-Sheet 2 \M \Q 5 g Q Q; O 2 L \5 k m1/ m E? If! E Q \5 L p v 0 3 N Y 5 2 8 c 0 m2 cg/ 3 Q 9 Q Q E n l o\ oj1 INVE NTOQ Philip Cooke Bish p ATTOE NEVO United States Patent MACHINEAND METHOD FOR THE PRODUCTION OF BLASTING DETONATORS AND IDIPROVEDBLASTING DETONATORS Philip C. Bishop, Saitcoats, Scotland, aasignor toImperial Chemical industries Limited, a corporation of Great BritainApplication May 22, 1951, Serial No. 227,574

Claims priority, application Great Britain June 2, 1950 3 Claims. (CI.86-69) The present invention relates to an improved method and machinefor the production of blasting detonators of the kind wherein a portionof the wall of the ductile metal casing in the vicinity of the mouth ispressed against a closure member of a resiliently deformable natureinserted into the mouth of the casing, and to improved detonators madethereby.

The invention is applicable for instance to the manufacture of theso-called capped fuses which consist essentially of a plain detonatorfirmly attached to a length of safety fuse extending from the exteriorthrough the mouth of the detonator casing so that one end of it is inclose proximity to the detonator charge, and also to the production ofelectric detonators of the kind in which a portion of the detonatorcasing in the vicinity of the mouth is forced into contact with aresiliently deformable plug through which pass insulated conductorsleading to an electric igniter positioned within the casing for ignitionof the detonator charge.

Hitherto in the production of capped fuses and in the main of electricdetonators of the kind described the method of attachment of thedetonator casing to the resilient element inserted through its mouth hasconsisted in crimping the metal of the detonator casing into contactwith the said resilient member, by which we mean that a tool is appliedto the exterior of the detonator casing that has the efiect of makingsharp indentations around the periphery of that portion of the casing,in order to ensure that the detonator and the element protruding fromit, i. e. the fuse or the conductors, will not easily be torn apart fromone another.

Various types of crimp are used in practice, and depending in part onthe mechanical strength and the degree of waterproofness of the assemblyrequired, the number and position of the indentations in the area wherethey are made shows considerable variation, but it is always acharacteristic of the method of crimping that the metal of the casingundergoes sharp distortions, which constitute a mechanical weakness.Thus the sharp distortions of the metal may lead to the development ofcracks in the metal of the casing especially if the metal is not ofuniform physical properties, and their existence may escape notice, withthe result that the waterproof properties of the detonator suffer, withconsequent risk of failure to function even if the mechanical strengthof the assembly appears to be satisfactory. v

According to the present invention the method for providing a detonatorwith a resilient closure member comprises necking the mouth portion ofthe detonator casing on to the closure member.

if desired the closure member is of smaller diameter than the diameterof the mouth portion of the detonator casing before necking.

Furthermore if desired the closure member passes through the mouth ofthe detonator and can be for example a length of safety fuse.

By neck is to be understood a portion of a detonator 2,773,410 PatentedDec. 11, 1956 tube having a reduced diameter and at least approximatelythe original circular cross-section.

In the resulting detonators where the surface of the metal of the casingpresses into contact with the resilient member there are no places wherethe metal is doubled back on itself. Thus the liability to thedevelopment of cracks or weaknesses in the metal is greatly reduced, andthe mechanical strength and waterproofness of the joint are highlysatisfactory. In fact the waterproofness attainable can be greater thanis necessary for most purposes. For example it has been experimentallyascertained that the said joints can withstand an external waterpressure of 200 lbs./ sq. inch without leakage.

It will be understood that the contour of the necked surface may bevaried for instance by providing two or more necks connected by surfacesof gradually or progressively diminishing diameter towards the month endof the detonator.

A detonator according to the present invention therefore has a neck inthe mouth portion of the detonator casing and a resilient closure memberin said neck.

If desired the resilient closure member passes through the mouth of thedetonator casing as for example where the resilient closure member is alength of safety fuse.

Apparatus according to the present invention comprises a pusher incombination with a die formed from two portions which are adapted to bemoved apart and to be brought together by movements having components atright angles to the path of said pusher and when apart to besufliciently separated to allow a detonator to be inserted or withdrawnfrom its forward end and when together to leave a small axial opening atits forward end and to form at least one surface progressivelyconverging forwardly, said pusher being positioned at the rearward endof said die.

If desired the said two portions when together form a longitudinalchannel commencing at the rearward end of the die.

One form of apparatus suitable for the production of detonatorsaccording to the invention comprises longitudinally reciprocableportions which in their forward position form together an axiallychannelled exteriorly frustoconical die having at least one internalsurface progressively converging forwardly and a small axial opening atits forward end and in their reaward position have a separationsuificient to aliow a detonator to be inserted or withdrawn through theforward end, a fixed annular guide having a frusto-conical surfaceadapted to bring together said die portions moving forwardly within itto support said portions over the area of their frusto-conical surfacewhen in the forward position, springs adapted to separate said dieportions as they move backwards within said annular guide, an axiallychannelled stem attached to said die of suificient diameter toaccommodate a detonator tube, and a reciprocating pusher.

Preferably the reciprocating pusher is timed with the motion of saidstem so as to permit a detonator tube to fall into the channel of saidstem when said stem and die portions are in retracted position and topush the detonator tube forward during the forward motion of said stemand die portions.

In accordance with this form of apparatus the stern of the die isslotted so that when said stem and the pusher are in retractedpositionthe slot is in line with a supply of longitudinally orientatedand superposed detonator tubes forwardly of the pusher.

If it is desired that the necked portion of the detonator should havetwo or more necks connected by surfaces of gradually or progressivelyforwardly converging contour they may either all be formed in a singleoperation by suitably contouring the forward portion of the channel ofthe die portions or the machine may incorporate a pin.

rality of units whereof the die channels are each formed with one of thedesired contours, and if desired it may be arranged that the detonatornaked on the first unit may be transferred to the die of the next unitin its open position by suitable means. v

if it is desired to produce a smaller neck than can conveniently be donein one operation then an assembly can be provided consisting ofsuccessive apparatus each having a die of larger diameter than the nextone and means to enable detonators to be transferred from one saidapparatus to its next one.

The apparatus of the invention may be set either horizontally orvertically, and where there is used a loose igniting charge instead of amatchhead would be set vertically so that the mouth of the detonatortube points upwards.

One form of apparatus according to the invention is illustrated byreference to the diagramamtic drawings accompanying the specificationwhereof Fig. l is a longitudinal axial section in a vertical planeshowing the die in its closed position with a necked detonator enclosedtherein at the end of a working stroke. Fig. 2 is a similar sectionshowing the die in its open position with the pusher retracted and adetonator tube in front of the pusher and also an electric fuse assemblyhaving its-leading wires passing through a resilient plug ready to beassembled with the detonator tube. Fig. 3 is an end elevation as seenfrom the front of a portion of the apparatus illustratcd in Fig. 2 andFig. 4 is a similar end elevation corresponding to Fig. 1. Fig. is alongitudinal axial section in a horizontal plane corresponding toFig. 1. Fig. 6 is a detail showing the shape of a die having twotapering portions and Fig. 7 is a detail showing a finished electricdetonator, these two figures being on a larger scale than Figs. l-5.

in Figs. 1-5, 1 is the body of the machine and 2 a flange thereonproviding a base for the machine. 3 are parallel arms formed integralwith an annular guide 4 having a frusto-conical internal surface. 5 is ahorizontally split externally frusto-conical die the halves of which aresemi-cylindrically axially channeled for the greater part of theirlength and at their forward portion are so contoured as to provide whenthe die is closed a channel of the desired shape for the neckeddetonator, terminating in a somewhat flaring mouth. These portions ofthe die are drilled with vertical holes 6 near their centre of gravityso as to accommodate springs 7 normally in compression tending to urgethe two halves apart from one another. These portions of the die aredove-tailed into an axially channelled reciprocable stem 8 whichprevents the halves of the die from relative motion horizontally butpermits them to move apart from one another in a vertical plane, thisstem having integral rearward extension forks 9 in which cross-head 11is reciprocated axially by a power operated piston. 31 is a flanged ringjoining the end of the forks 9 and providing a stop for the crosshead11. When the piston is retracted this cross-head pulls back the forks 9and the integral stem 8 and with them the halves of the die 5 and theseare forced apart during this motion by the springs 7. The frusto-conicalshape of the exterior of the die 5 and the internal surface of theconstrictor guide 4 are of the same taper and maintain the halves of thedie in parallel relation. The flanged ring 31 during its rearward motionalso compresses a spring 12 against an outer bearing 13. A slot 14 isprovided in the body 1 through which a bolt 15 is screwed into a channeldrilled in one of the forks 9 so as to prevent the stem 8 from rotatingin a vertical plane. 16 is another slot in the body forming part of thetermination of a magazine chamber. 17 is a slot in the stem 8 from whicha detonator tube falls into the axial channel thereof when the piston 10is retracted, and into which another detonator fails when retraction ofthe stem .8

rearward and their open ends forward. 20 is acoupling head 11 and piston10. 21 is an adjustable stop motion nut.

The electric fuse assembly consisting of insulated leading Wires 22passing through a cylindrical plug 24 of resiliently deformablerubber-like material and terminating in a matchhead 23 is introducedinto the die from the front in its retracted position and may be heldapproximately in the desired position beyond the converging portion. Thesucceeding forward stroke of the die causes its halves to come togetherand thus traps the plug 24 beyond the converging portion of the die. Thedie however does not necessarily grip the plug tightly. The forwardstroke of the piston behind the detonator tube 19 ultimately causes themouth of the detonator tube to reach the plug and carry it forward untilit meets resistance due to the convergence of the die. The tube mouththen rides over the plug and grips it when forced into theconvergingportion of the die. The tube and plug then advance togetherthrough the narrow portion of the die, thus forming the neck containingthe plug. The original position of the plug in the channel is thereforea matter of indifference as long as it is beyond the converging portionof the channel. The retraction of the piston and with it the die enablesanother detonator tube to fall into position in the channel of the stem8 and'opens up the die and enables the necked detonator tube to bewithdrawn from the front.

In Fig. 6 the contour of the cylindrical part of the die channel isshown by 25, that of one of the converging portions by 26, which givesplace to a smaller cylindrical portion 27 and then to a smallerconverging portion 28 leading to an even smaller cylindrical portion 29which is outwardly flared as shown at 30.

What I claim is:

1. Apparatus for closing the open end of a detonator tube around aresilient closing element comprising a divided die mounted for movementbetween an open position and a closed position, said die in its closedposition defining a channel having a longitudinally ex-' tendingdetonator tube receiving portion and an inwardly tapered portioncommunicating therewith, means for moving said die into its closedposition, means movable through an operative path for effecting arelative longitudinal movement between said die and a detonator tubepositioned adjacent thereto, means operatively associated with saidrelative movement effecting means and said die closing means foractuating the latter to close said die in response to the initialmovement of said relative movement effecting means through saidoperative path, said relative movement effecting means being oper- Iable upon further movement through said operative path to effect aninterengaging relative longitudinal movement between the inwardlytapered portion of said die channel and the open end of the detonatortube so as to deform the latter inwardly into engagement with aresilient closing element disposed therein.

2. Apparatus for closing the open end of a detonator tube around aresient cl .ing element comprising a divided die movable betwe .n anopen position and a closed position, guide means receiving said die, adriving member connected with said die for reciprocating the latterwithin said guide means to effect the movement of said die into its openand closed positions, said die in its closed position defining a channelhaving a detonator tube receiving portion and an inwardly taperedportion communicating therewith, a plunger slidably mounted within saiddriving member for movement toward and away from said die, and meansoperatively connected between said plunger and said driving member formoving the latter to effect the movement of said die into its closedposition in response to the initial movement of said plunger toward saiddie, said plunger bebrings said slot 17 into alignment with slot 16. The

detonator tubes 19 are presented with their closed ends ing operableupon further movement thereof toward said die to force the open end ofa-detonator tube disposed within the receiving portion of the diechannel into engagement with the inwardly tapered portion thereofwhereby the open end is deformed inwardly into engagement with aresilient closing element disposed therein.

3. Apparatus as defined in claim 2 wherein said die comprises a pair ofdie elements having a spring therebetween normally urging the sameradially apart and wherein the inner end of each die element isconnected with said driving member by means of a dove tail connectionoperable to prevent relative longitudinal movement between the dieelements and the driving member and to permit radial movement of the dieelements with respect to each other.

References Cited in the file of this patent UNITED STATES PATENTS

